Polythiophene (PTh)-TiO2-Reduced Graphene Oxide (rGO) Nanocomposite Coating: Synthesis, Characterization, and Corrosion Protection Performance on Low-Carbon Steel in 3.5 wt % NaCl Solution.

Abstract

The ternary nanocomposite polythiophene (PTh)-TiO2-reduced graphene oxide (rGO) (PTh-TiO2-rGO) was synthesized by chemical oxidative polymerization with FeCl3 used as the oxidizing agent. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the synthesized nanocomposite, followed by its casting on a low-carbon steel (LCS) substrate using N-methyl-2-pyrrolidone (NMP) as a solvent and an epoxy resin and triethyl tetraamine as a binder and curing agent, respectively. Anticorrosion properties of the PTh-TiO2-rGO nanocomposite in 3.5 wt % NaCl solution were established using open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), salt spray test, immersion test, contact angle (CA) measurements, water uptake test, and SEM. Additionally, PTh and PTh-TiO2 were separately synthesized, characterized, and subjected to anticorrosion tests following identical synthesis routes for comparison purposes. The results of the investigations demonstrated that the PTh-TiO2-rGO nanocomposite coating provides superior protection in 3.5 wt % NaCl solution compared to pure PTh and PTh-TiO2 coatings, which are evident from its lowest corrosion current density (I corr) (0.570 × 10-6 A cm-2), highest positive shift in corrosion potential (E corr) (-0.578 V), highest impedance and phase angle (3.56 × 103 Ω cm2 and 70°, respectively), highest hydrophobicity (CA 94°), and highest protection efficiency (99%). These results show that the proposed nanocomposite coating provides better corrosion protection in a 3.5 wt % NaCl solution than other coatings.